Rotary Pump And Multiple Rotary Pump Employed Thereof

ABSTRACT

A rotary pump is provided in which a drive motor is provided such that an output shaft of the drive motor is placed at an offset position, so that a rotational speed of the pump can be changed to a high or low speed. Furthermore, rigid balls or needle roller bearings are used in each rotor unit such that each eccentric rotary body is in rolling contact with a circumferential inner surface of each cylindrical housing, thus reducing friction between them, thereby ensuring smooth rotation of the rotor units. In addition, a space, which is defined between each cylindrical housing and each eccentric rotary body, prevents a cross-plate from being damaged due to torsional stress and tensile force, thereby ensuring superior durability of the pump.

CROSS-REFERENCE(S) TO RELATED APPLICATION(S)

The present application is based on, and claims priority from, Korean Patent Application Serial Numbers 2004-0114504, 2005-0001006, 2005-0090212, and 2005-0090214.

BACKGROUND

1. Technical Field

The present invention relates, in general, to rotary pumps which pump fluid using suction force of rotor units that are rotated by drive motors and, more particularly, to a multiple rotary pump in which a drive motor is provided such that an output shaft of the drive motor is placed at an offset position, so that a rotational speed of the pump can be changed to a high or low speed, and in which an eccentric rotary body is moved in a space defined in each rotor unit, thus preventing a cross-plate from being damaged, and which ensures smooth rotation of the rotor units using a bearing means.

2. Description of the Related Art

As well known to those skilled in the art, pumps are machines which move fluid to another place, for example, from a low position to a high position.

However, conventional pumps have many problems. Hereinafter, a representative conventional pump will be explained, and problems experienced with this pump will be described.

FIG. 1 illustrates a rotary pump in which an upper rotor unit 2, which is provided in an upper chamber 1, is coupled to a lower rotor unit 4, which is provided in a lower chamber 3, through a cross-plate 5.

As shown in FIG. 1, in the conventional rotary pump, when the upper rotor unit 2 and the lower rotor unit 4 are placed upright, the distance between the centers of the upper and lower rotor units 2 and 4, which are offset from the chambers, is shortest.

In other words, the distance between the upper rotor unit 2 and the lower rotor unit 4 becomes shortest.

As shown in the second view of FIG. 1, when the upper rotor unit 2 and the lower rotor unit 4 are placed in an oblique direction, the distance between the centers of the upper and lower rotor units 2 and 4, which are offset from the chambers, is longest.

In other words, the distance between the upper rotor unit 2 and the lower rotor unit 4 becomes longest.

For example, as shown in FIG. 1, when the upper rotor unit 2 and the lower rotor unit 4 are placed upright, the distance between the centers of the upper and lower rotor units 2 and 4, which are offset from the chambers, is 6.90 inches (175.2 mm).

At this time, the distance between the upper rotor unit 2 and the lower rotor unit 4 is 2.41 inches (61.2 mm). As shown in FIG. 1, when the upper rotor unit 2 and the lower rotor unit 4 are placed in an oblique direction, the distance between the centers of the upper and lower rotor units 2 and 4, which are offset from the chambers, is 6.98 inches (177.2 mm).

At this time, the distance between the upper rotor unit 2 and the lower rotor unit 4 is 2.49 inches (63.2 mm).

Here, if the cross-plate 5, which couples the upper rotor unit 2 to the lower rotor unit 4, is a rigid body, the structure and operation of the rotary pump shown in FIG. 1 cannot be realized. In other words, the length of the cross-plate 5 must be varied depending on the positions of the rotor units 2 and 4.

To solve the above-mentioned problem, a rotary pump was proposed in Korean Patent Application No. 1994-010299, entitled “double cylindrical pump.”As shown in FIG. 2, this pump is constructed such that a cross-plate 3 is inserted into a sliding slot 2 formed in a circumferential outer surface of a first sliding body 1 (hereinafter, referred to as an upper rotor unit), and the cross-plate 3 is removably coupled to the upper rotor unit 1 and is integrally coupled to a second sliding body 4 (hereinafter, referred to as a lower rotor unit).

Thus, when the upper rotor unit 1 and the lower rotor unit 4 are placed in an oblique direction, the cross-plate 3 slides in the sliding slot 2 of the upper rotor unit 1, so that the distance between the upper rotor unit 1 and the lower rotor unit 4 can be varied. However, in this pump, in which the distance between the upper and lower rotor units 1 and 4 is varied by the cross-plate 3 moving in the sliding slot 2 of the upper rotor unit 1, because the cross-plate 3 slides in the sliding slot 2 while the upper and lower rotor units 1 and 4 are rotating, there is a likelihood of the cross-plate 3 being undesirably removed from the upper rotor unit 1. Furthermore, in the case that this pump structure is applied to a multiple rotary pump, because rotational force (torque) is applied to the upper rotor unit 1 prior to sliding movement of the cross-plate 3 in the sliding slot 2, torsional stress is applied to offset shafts which rotate the upper rotor unit 1.

Of course, this phenomenon may cause breakage of the offset shafts, the rotor units 1 and 4 or the cross-plate 3.

To solve this problem, a method in which eccentric gears are used to constantly maintain the distance between upper and lower rotor units has been used. However, in the case that this method is applied to a multiple rotary pump, the offset shafts rotate the upper rotor unit in a clockwise direction and rotate the lower rotor unit in a counterclockwise direction using the eccentric gears, thus generating torsional stress. As such, the eccentric gears can be used in a rotary pump having a single structure, but, in the case that the eccentric gears are used in a multiple rotary pump, because the orientations of the rotor units coupled to the shafts are different, an acceleration section is varied by the eccentricity. Thus, the possibility of breakage of the rotor units is increased.

BRIEF SUMMARY

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a multiple rotary pump which pumps fluid using suction force of rotor units rotated by a drive motor, and in which the drive motor is provided such that an output shaft of the drive motor is placed at an offset position, so that a rotational speed of the pump can be changed to high or low speed, and in which an eccentric rotary body is moved in a space defined in each rotor unit, thus preventing a cross-plate from being damaged, and which ensures smooth rotation of the rotor units using a bearing means.

In one embodiment, the present invention provides a rotary pump which has a drive motor and upper and lower chambers and pumps fluid both using rotor units moving along inner surfaces of the chambers and using a cross-plate. The rotary pump comprises: a drive motor provided at a predetermined position such that an output shaft thereof is disposed at an offset position, with an overload prevention unit provided on an end of the output shaft, the overload preventing unit having a helical motor gear; a clutch unit coupled to an end of the overload prevention unit; upper and lower chambers; rotor units provided in the respective upper and lower chambers such that power is transmitted through the clutch unit to the rotor units, each of the rotor units having an eccentric rotary body installed in each rotor unit and eccentrically rotated by each of a pair of rotating shafts and, with bearing means provided in each of the rotor units. When power of the drive motor is transmitted, the number of revolutions of the drive motor is changed by the clutch unit, and the rotor units move along inner surfaces of the chambers using the power transmitted through the clutch unit, thus pumping fluid from the chambers.

The clutch unit, is coupled to the overload prevention unit, and may comprise: a first gear engaging with the helical motor gear, which is eccentrically positioned, the first gear being rotatably fitted over one of the rotating shafts, which is placed at a position opposite a direction in which the helical motor gear is offset, and a first subsidiary gear having a diameter smaller than a diameter of the first gear and integrally provided beneath the first gear; a second gear having a larger diameter and engaging with the first subsidiary gear, the second gear being rotatably fitted over the other of the rotating shafts, and a second subsidiary gear having a diameter smaller than the diameter of the second gear and integrally provided beneath the second gear; a third gear having a larger diameter and engaging with the second subsidiary gear, the third gear being rotatably fitted over the one of the rotating shafts, and a third subsidiary gear having a diameter smaller than the diameter of the third gear and integrally provided beneath the third gear; a fourth gear having a larger diameter and engaging with the third subsidiary gear, the fourth gear being rotatably fitted over the other of the rotating shafts, and a fourth subsidiary gear having a diameter smaller than the diameter of the fourth gear and integrally provided beneath the fourth gear; a fifth gear having a larger diameter and engaging with the fourth subsidiary gear, the fifth gear being rotatably fitted over the one of the rotating shafts, and a fifth subsidiary gear having a diameter smaller than the diameter of the fifth gear and integrally provided beneath the fifth gear; a drive gear having a larger diameter and engaging with the fifth subsidiary gear, the drive gear being fitted over and locked to the other of the rotating shafts using a key; and first and second main gears having a same diameter and respectively fitted over and locked to the rotating shafts and using keys, respectively. When the first, second, third, fourth and fifth gears and the first, second, third, fourth and fifth subsidiary gears are fitted over the first and second shafts, bearings are interposed between the rotating shafts and the gears such that the gears are rotated at relatively low speeds with respect to the rotating shafts, and when the first and second main gears and are rotated at low speeds by the power transmitted from the drive gear, the rotor units are rotated at low speeds.

In another embodiment of the clutch unit coupled to the overload prevention unit, the clutch unit comprises: a first gear engaging with the helical motor gear, which is eccentrically positioned, the first gear being rotatably fitted over one of the rotating shafts, which is placed at a position opposite a direction in which the helical motor gear is offset, and a first subsidiary gear having a diameter larger than a diameter of the first gear and integrally provided beneath the first gear; a second gear having a smaller diameter and engaging with the first subsidiary gear, the second gear being rotatably fitted over the other of the rotating shafts, and a second subsidiary gear having a diameter larger than the diameter of the second gear and integrally provided beneath the second gear; a third gear having a smaller diameter and engaging with the second subsidiary gear, the third gear being rotatably fitted over the one of the rotating shafts, and a third subsidiary gear having a diameter larger than the diameter of the third gear and integrally provided beneath the third gear; a fourth gear having a smaller diameter and engaging with the third subsidiary gear, the fourth gear being rotatably fitted over the other of the rotating shafts, and a fourth subsidiary gear having a diameter larger than the diameter of the fourth gear and integrally provided beneath the fourth gear; a drive gear having a smaller diameter and engaging with the fourth subsidiary gear, the drive gear being fitted over and locked to the one of the rotating shafts using a key; and first and second main gears having a same diameter and respectively fitted over and locked to the rotating shafts using keys. When the first, second, third and fourth gears and the first, second, third and fourth subsidiary gears are fitted over the first and second shafts, bearings are interposed between the rotating shafts and the gears such that the gears are rotated at relatively high speeds with respect to the rotating shafts, and when the first and second main gears are rotated by the power transmitted from the drive gear, the rotor units are rotated at high speeds.

Each of the rotor units may comprise: a cylindrical housing having a cylindrical shape with a diameter smaller than an inner diameter of each chamber, with a plurality of bearing seats formed in a circumferential inner surface of the cylindrical housing, and a space defined in the cylindrical housing; the eccentric rotary body having a diameter smaller than the inner diameter of the cylindrical housing and eccentrically fitted over each of the rotating shafts; and the bearing means seated into the bearing seats of the cylindrical housing. Both the cylindrical housing and the eccentric rotary body are provided in each of the upper and lower chambers, and the two cylindrical housings are coupled to each other through the cross-plate and are eccentrically rotated.

In another embodiment, each rotor unit may comprise: a cylindrical housing having a cylindrical shape with a diameter smaller than an inner diameter of each chamber, with a space defined in the cylindrical housing; the eccentric rotary body having a diameter smaller than the inner diameter of the cylindrical housing and eccentrically fitted over each of the rotating shafts, with a plurality of bearing seats formed in a circumferential outer surface of the eccentric rotary body; and the bearing means seated into the bearing seats of the eccentric rotary body. Both the cylindrical housing and the eccentric rotary body are provided in each of the upper and lower chambers, and the two cylindrical housings are coupled to each other through the cross-plate and are eccentrically rotated.

As described above, in the rotary pump according to an embodiment of the present invention, rigid balls or needle roller bearings serving as a bearing means are used in each rotor unit such that each eccentric rotary body is in rolling contact with the a circumferential inner surface of each chamber, thus reducing friction between them, thereby ensuring smooth rotation of the rotor units.

Furthermore, in embodiments of the present invention, a space is defined between the chamber and the eccentric rotary body, thus solving a conventional problem in that a cross-plate is damaged by torsional stress and tensile force, thereby ensuring superior durability of the pump.

As well, even if an overload is applied to the rotor units or a clutch unit, because an overload prevention unit is provided, the clutch unit is prevented from being damaged, thus further enhancing the durability.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a view showing a rotor unit of a conventional rotary pump;

FIG. 2 is a view showing a cross-plate inserted into a slide slot of a rotor unit of another conventional pump;

FIG. 3 is a view showing an operation of a rotor unit according to one embodiment;

FIG. 4 is a schematic view showing a reason that a cross-plate must be lengthened;

FIG. 5 is a sectional view showing a first embodiment of a clutch unit of the present invention;

FIG. 6 is a sectional view showing a second embodiment of a clutch unit of the present invention;

FIG. 7 is a sectional view showing a third embodiment of a clutch unit of the present invention;

FIG. 8 is a sectional view showing a fourth embodiment of a clutch unit of the present invention;

FIGS. 9 and 10 are views showing an operation of a rotor unit according to one embodiment;

FIG. 11 is a view showing an enlargement of a first embodiment of a rotor unit of the present invention;

FIG. 12 is a view of a cylindrical housing according to the first embodiment of the rotor unit of the present invention;

FIG. 13 is a schematic view illustrating an operation of the rotor unit according to the first embodiment of the present invention;

FIG. 14 is a view showing a modification of the rotor unit according to the first embodiment of the present invention;

FIG. 15 is a view showing an enlargement of a second embodiment of the rotor unit of the present invention;

FIG. 16 is a view showing an eccentric rotary body according to the second embodiment of the rotor unit of the present invention;

FIG. 17 is a view showing a modification of the rotor unit according to the second embodiment of the present invention;

FIG. 18 is a schematic view illustrating an operation of the rotor unit according to the second embodiment of the present invention;

FIG. 19 is schematic views showing installation of a bearing means according to one embodiment of the present invention;

FIG. 20 is schematic views showing installation of the bearing means according to one embodiment of the present invention;

FIG. 21 is a plan view of a pump according to one embodiment of the present invention;

FIG. 22 is a view showing a duplex pump according to one embodiment of the present invention;

FIG. 23 is a view showing a triplex pump according to one embodiment of the present invention;

FIG. 24 is a view showing a quadruple pump according to one embodiment of the present invention;

FIG. 25 is a view showing an example of a piping structure of a pump according to one embodiment of the present invention;

FIG. 26 is a view showing another example of a piping structure of a pump according to one embodiment of the present invention;

FIG. 27 is a view showing a further example of a piping structure of a pump according to one embodiment of the present invention;

FIG. 28 is a view showing yet another example of a piping structure of a pump according to one embodiment of the present invention;

FIG. 29 is a sectional view showing the construction of the quadruple pump according to one embodiment of the present invention;

FIG. 30 is a perspective view of an overload prevention unit of one embodiment of the present invention; and

FIG. 31 is a sectional view showing the overload prevention unit coupled to an output shaft of a drive motor according to one embodiment of the present invention.

DETAILED DESCRIPTION

According to one embodiment, a rotary pump includes a drive motor and upper and lower chambers, in which a pumping operation is executed by movement both of rotor units, which rotate along the inner surface of the chambers, and of a cross-plate. The rotary pump further includes an eccentric rotary body in each rotor unit, and a gap is defined between the rotor unit and the eccentric rotary body. Thanks to the gap, embodiments of the present invention do not require a variable length of the cross-plate, unlike the conventional art. Furthermore, another special feature of the present invention is characterized in that a rotational speed can be changed between a high speed and a low speed. Hereinafter, the present invention will be described in detail with reference to the attached drawings. To explain the present invention more clearly, an operation of the rotor units will be described with reference to FIG. 3.

According to one embodiment, a rotary pump includes a pair of rotor units 200 which rotate in two chambers 30, which can be circular in shape.

As shown in FIG. 3, an upper rotor unit 200 (placed at an upper position when viewing the drawing) is rotated in a clockwise direction. A lower rotor unit 200 (placed at a lower position when viewing the drawing) is rotated in a counterclockwise direction. Therefore, as sequentially shown in FIG. 3, first, the rotor units 200 are oriented in a vertical direction while the upper rotor unit 200 contacts the uppermost point of an upper chamber 30. Next, the upper rotor unit 200 is rotated at 90° in a clockwise direction, so that the contact surface of the upper rotor unit 200 moves to a portion of the upper chamber 30 (placed at the upper position when viewing the drawing) which is spaced apart from the uppermost point at 90°. Of course, at this time, the lower rotor unit 200 (placed at the lower position when viewing the drawing) is rotated at 90° in a counterclockwise direction so that the contact surface thereof moves to a portion of the inner surface of the lower chamber 30 (placed at the lower position when viewing the drawing) which is spaced apart from the uppermost point at 270°.

Subsequently, the upper rotor unit 200 is rotated in a clockwise direction until it reaches a portion of the upper chamber 30 spaced apart from the uppermost point at 180°. At this time, the lower rotor unit is rotated in a counterclockwise direction until it reaches a portion of the inner surface of the lower chamber 30 spaced apart from the uppermost point at 180°.

Continuously, the upper rotor unit 200 is rotated in a clockwise direction until it reaches a portion of the inner surface of the upper chamber 30 spaced apart from the uppermost point at 270°. Simultaneously, the lower rotor unit is rotated in a counterclockwise direction until it reaches a portion of the inner surface of the lower chamber 30 spaced apart from the uppermost point at 90°. Of course, after that, the rotor units 200 are returned to the first stage. This process is continuously repeated.

In another embodiment, unlike the above case in which the upper rotor unit 200 is rotated in a clockwise direction while the lower rotor unit 200 is rotated in a counterclockwise direction, the upper rotor unit 200 may be rotated in a counterclockwise direction, and the lower rotor unit 200 may be rotated in a clockwise direction.

In either case, by such rotation, fluid is drawn into the chambers 30 through an inlet (BC) and is discharged through an outlet (BD).

Hereinafter, the reason that a cross-plate 207 that couples the upper rotor unit 200 to the lower rotor unit 200 must be lengthened and shortened when the rotor units 200 are rotated in the conventional art, will be explained with reference to FIG. 4.

For ease of description, in this drawing, the diameter of each rotor unit 200 is greatly reduced.

As shown in the drawing, in the conventional art, when the upper rotor unit 200 and the lower rotor unit 200 are disposed in a vertical line, the length of the cross-plate is AB and the same as the length AC (AB=AC).

Meanwhile, when the upper rotor unit 200 is rotated in a clockwise direction and reaches the portion of the inner surface of the upper chamber 30 spaced apart from the uppermost point at 90°, the lower rotor unit 200 is rotated in a counterclockwise direction and reaches the portion of the inner surface of the lower chamber 30 spaced apart from the uppermost point at 270°.

At this time, the length of the cross-plate is AK. Therefore, as demonstrated in the Pythagorean Theorem in that the length of the hypotenuse of a right-angled triangle is longest, the length of the cross-plate must be lengthened by any method.

For this, the conventional art has the structure such that the length of the cross-plate is varied while the diameter of the rotor unit 200 is constant.

Meanwhile, as the problems of the conventional art have already been described above, further explanation is deemed unnecessary. To solve the problems of the conventional art, in embodiments of the present invention, an eccentric rotary body 220 is provided in each rotor unit 200, and a space is defined around the eccentric rotary body in the rotor unit 200. The description of these is as follows.

According to one embodiment, shown in FIG. 5 a drive motor 10 is provided at a predetermined position such that an output shaft 11 thereof is disposed at an eccentric position. An overload prevention unit 20 having a helical motor gear 12 is provided toward an end of the output shaft 11. A clutch unit 100 is provided on an end of the overload prevention unit 20. Furthermore, chambers 30 are provided at upper and lower positions. The rotor units 200, which receive driving force from the clutch unit 100, are installed in the chambers 30. The eccentric rotary body 220, which has a bearing means 210 and is rotated by a rotating shaft S1 or S2, is installed in each rotor unit 200.

Therefore, while power of the drive motor 10 is transmitted to the rotating shafts S1 and S2, revolutions of the rotating shafts S1 and S2 are changed by the clutch unit 100. Fluid is pumped outside of the chambers 30 by pumping-rotation of the rotor units 200.

In detail, the drive motor 10 is coupled to the pump such that the output shaft 11 thereof is positioned toward a side of the center of the pump, that is, is eccentrically positioned with respect to the pump. Furthermore, the helical motor gear 12 is provided toward the end of the output shaft 11 to increase rotating friction.

The clutch unit 100 is coupled to the helical motor gear 12. In embodiments of the present invention, a high-speed clutch unit 100 or a low-speed clutch unit 100, which will be explained later herein, can be selectively provided.

According to one embodiment, rotational force of the drive motor 10 is transmitted to the rotating shafts S1 and S2 through the clutch unit 100, after the rotational speed is changed to a high or low speed by the clutch unit 100. The eccentric rotary bodies 220 are rotated by the above-mentioned rotational force. At this time, the eccentric rotary bodies 220 can be smoothly rotated by the bearing means 210 during the fluid pumping operation.

Hereinafter, embodiments of the clutch unit 100 used in the present invention will be described.

In the case of a first embodiment, as shown in FIG. 5, the clutch unit 100 is coupled to the overload prevention unit 20. In detail, a low-speed drive gear 110, which engages with the helical motor gear 12 that is eccentrically positioned, is fitted over the rotating shaft S2, which is placed at a position opposite the direction in which the helical motor gear 12 is offset. The low-speed drive gear 110 is locked to the rotating shaft S2 by a key K. A first main gear 111 is fitted over the rotating shaft S2 below the low-speed drive gear 110 while being locked to the rotating shaft S2 by a key K.

Furthermore, a second main gear 112, which engages with the first main gear 111, is fitted over the other rotating shaft S1 and locked to the rotating shaft S1 by a key.

Therefore, the first main gear 111 is rotated by rotation of the low-speed drive gear 110 at a low speed. The second main gear 112, which engages with the first main gear 111, is rotated in an opposite direction.

As shown in FIG. 5, the drive motor 10 is provided such that the output shaft 11 thereof is inserted into the pump at an offset position, in detail, at a position offset towards the upper rotor unit 200 (located on the right when viewing the drawing).

Of course, the output shaft 11 may be eccentrically placed such that it is offset towards the lower rotor unit 200 (located on the left when viewing the drawing).

As shown in this embodiment, the reason that the output shaft 11 is placed such that it is offset towards the upper rotor unit 200 is to construct the rotary pump such that the rotational speed of the rotating shafts S1 and S2 can be changed to a high or low speed. If the output shaft 11 is offset towards the upper rotor unit 200, a space defined between the output shaft 11 and the lower rotor unit 200 (located on the left when viewing the drawing) is greater than a space defined between the output shaft 11 and the upper rotor unit 200.

Therefore, as shown in FIG. 5, the gear having a larger diameter can be applied in the larger space.

As well known in the art, when a small gear rotates a large gear, the rotational speed of the shaft of the large gear becomes slower than that of the small gear. Therefore, in the first embodiment of FIG. 5, the low-speed drive gear 110 is rotated at a low speed. In other words, when the drive motor 10 is rotated, the low-speed drive gear 110, having the large diameter, is rotated at a low speed.

Of course, because the low-speed drive gear 110 is locked to the rotating shaft S2 by the key K, the rotating shaft S2 and the low-speed drive gear 110 are rotated at the same angular speed.

Furthermore, the first main gear 111 is locked to the rotating shaft S2 by the key K below the low-speed drive gear 110. Therefore, revolutions of the low-speed drive gear 110 are also the same as that of the rotating shaft S2.

Furthermore, the second main gear 112, which engages with the first main gear 111, is locked to the other rotating shaft S1 by a key. The rotating shafts S1 and S2, which are coupled to the clutch unit 100, are coupled to the respective eccentric rotary bodies 220 such that each eccentric rotary body 220 is eccentric.

As a result, the rotating shafts S1 and S2 are rotated in directions opposite each other and rotate the rotor units 200, thus pumping fluid at a low speed.

A pump according to embodiments of the present invention may be used for pumping air as well as fluid, that is, may be applied to a pneumatic compressor.

Meanwhile, FIG. 6 illustrates a high-speed type of a second embodiment of the clutch unit 100 of the present invention.

In this embodiment, a high-speed drive gear 120 is provided at the narrower side in the spaces defined between the rotating shafts S1 and S2 and the output shaft 11 of the drive motor 10, which is offset to the right when viewing the drawing. The high-speed drive gear 120 has a small diameter so that it can be rotated at a high speed.

A construction of this embodiment will be explained with reference to FIG. 6. In the second embodiment of the clutch unit 100 coupled to the overload prevention unit 20, the high-speed drive gear 120, which engages with the helical motor gear 12 that is eccentrically positioned, is fitted over the rotating shaft S1, which is placed at a predetermined position in the direction in which the helical motor gear 12 is offset. The high-speed drive gear 120 is locked to the rotating shaft S1 by a key K. A first main gear 121 is fitted over the rotating shaft S1 below the high-speed drive gear 120 while being locked to the rotating shaft S2 by a key K.

Furthermore, a second main gear 122, which engages with the first main gear 121, is fitted over the other rotating shaft S2 and locked to the rotating shaft S2 by a key K.

Therefore, the first main gear 121 is rotated by rotation of the high-speed drive gear 120 at a high speed. The second main gear 122, which engages with the first main gear 121, is rotated in an opposite direction.

The operation of the clutch unit 100 according to this embodiment will be explained with reference to FIG. 6. When the drive motor 10 is operated, the high-speed drive gear 120, which engages with the helical motor gear 12 coupled to the output shaft 11 of the drive motor 10, is rotated at a high speed.

Of course, the rotational speed of the high-speed drive gear 120 is slower than that of the output shaft of the drive motor 10. As such, when the high-speed drive gear 120 is rotated, the upper rotating shaft S1 (placed to the right when viewing the drawing), to which the high-speed drive gear 120 is locked by the key K, is rotated together. As well, the first main gear 121 is rotated at the same speed as that of the rotating shaft S1.

As shown in FIG. 6, because the second main gear 122 engages with the first main gear 121 which is locked to the rotating shaft S1 by the key K, the first main gear 121 and the second main gear 122 are rotated in substantially opposite directions at substantially the same angular speed.

In addition, because the second main gear 122 is locked to the rotating shaft S2 by the key K, the rotating shaft S2 is also rotated at substantially the same angular speed as that of the second main gear 122.

As a result, the rotor units 200, which are respectively coupled toward the ends of the rotating shafts S1 and S2 and form a single or multiple structure, are rotated by the rotation of the rotating shaft S2, thus executing the pumping operation.

A third embodiment of the clutch unit 100 of the present invention will be explained herein below with reference to FIG. 7.

In the third embodiment of the clutch unit 100 coupled to the overload prevention unit 20, a first gear 131, which engages with the helical motor gear 12 that is eccentrically positioned, is rotatably fitted over the rotating shaft S2, which is placed at a position opposite the direction in which the helical motor gear 12 is offset. A first subsidiary gear 132, having a diameter smaller than that of the first gear 131, is integrally provided beneath the first gear 131. A second gear 133, which has a relatively large diameter and engages with the first subsidiary gear 132, is rotatably fitted over the other rotating shaft S1. A second subsidiary gear 134, having a diameter smaller than that of the second gear 133, is integrally provided beneath the second gear 133. Furthermore, a third gear 135, which has a relatively large diameter and engages with the second subsidiary gear 134, is rotatably fitted over the rotating shaft S2. A third subsidiary gear 136, having a diameter smaller than that of the third gear 135, is integrally provided beneath the third gear 135. A fourth gear 137, which has a relatively large diameter and engages with the third subsidiary gear 136, is rotatably fitted over the other rotating shaft S1. A fourth subsidiary gear 138, having a diameter smaller than that of the fourth gear 137, is integrally provided beneath the fourth gear 137. As well, a fifth gear 139, which has a relatively large diameter and engages with the fourth subsidiary gear 138, is rotatably fitted over the rotating shaft S2. A fifth subsidiary gear 140, having a diameter smaller than that of the fifth gear 139, is integrally provided beneath the fifth gear 139. A drive gear 144, which has a relatively large diameter and engages with the fifth subsidiary gear 140, is fitted over the other rotating shaft S1 and locked to the other rotating shaft S1 by a key K.

Furthermore, first and second main gears 145 and 146, having substantially the same diameter, are respectively fitted over and locked to the other rotating shaft S1 and the rotary shaft S2 using keys K.

When the first, second, third, fourth and fifth gears 131, 133, 135, 137 and 139 and the first, second, third, fourth and fifth subsidiary gears 132, 134, 136, 138 and 140 are fitted over the first and second shafts S1 and S2, as discussed above, bearings B are interposed between them such that the gears are smoothly rotated at low speeds with respect to the rotating shafts S1 and S2. The first and second main gears 145 and 146 are rotated at low speeds by the rotational force transmitted through the drive gear 144, thus rotating the rotor units 200 at low speeds.

The operation of the third embodiment of the clutch unit 100 of the present invention will be explained herein below with reference to FIG. 7.

When the helical motor gear 12, which is offset to one side, is rotated, the first gear 131 having a relatively large diameter is rotated.

At this time, the rotational speed of the drive motor 10 decreases.

Here, the first subsidiary gear 132 is integrally provided beneath the first gear 131. The first subsidiary gear 132 has a diameter smaller than the diameter of the first gear 131.

Of course, because the first gear 131 and the first subsidiary gear 132 are integrated with each other, revolutions of them are equal to each other.

The first subsidiary gear 132 engages with the second gear 133 fitted over the upper rotating shaft S1 (located on the right side when viewing the drawing).

The first subsidiary gear 132 has a relatively small diameter, and the diameter of the second gear 133 is larger than that of the first subsidiary gear 132. Hence, when the rotational force is transmitted from the first subsidiary gear 132 to the second gear 133, the number of revolutions decreases.

Furthermore, the second subsidiary gear 134 is integrally provided beneath the second gear 133.

As such, the gears are integrated with each other, so that revolutions thereof are equal to each other.

The second subsidiary gear 134 engages with the third gear 135 fitted over the rotating shaft S2. Here, the third gear 135 has the diameter larger than that of the second subsidiary gear 134, so that the rotational speed is reduced when the rotational force is transmitted.

The third subsidiary gear 136, having the diameter smaller than that of the third gear 135, is integrally provided beneath the third gear 135.

As such, because the third gear 135 and the third subsidiary gear 136 are integrated with each other, revolutions thereof are equal to each other. The above-mentioned gear coupling structure is also applied throughout the fourth gear 137, the fourth subsidiary gear 138, the fifth gear 139 and the fifth subsidiary gear 140, so that the rotational speed is sequentially reduced. Furthermore, as shown in FIG. 7, the fifth subsidiary gear 140 engages with the drive gear 144 having a relatively large diameter. The drive gear 144 is locked to the upper rotating shaft S1.

Therefore, the upper rotating shaft S1 is rotated by the rotation of the drive gear 144. Meanwhile, because bearings B are provided around the rotating shafts S1 and S2 in the first, second, third, fourth and fifth gears 131, 133, 135, 137 and 139 and the first, second, third, fourth and fifth subsidiary gears 132, 134, 136, 138 and 140, they are smoothly rotated with respect to the rotating shaft to execute the functions of the speed reduction.

In other words, the rotating shaft S1 is rotated only by rotation of the drive gear 144. By this rotation, the first main gear 145, which is located on the right (when viewing the drawing), is rotated.

Of course, the number of revolutions of the first main gear 145 is equal to those of the drive gear 144 and the upper rotating shaft S1. Furthermore, the first main gear 145 engages with the second main gear 146. Hence, the second main gear 146 is rotated by the rotation of the first main gear 145 in a direction opposite that of the first main gear 145.

Furthermore, the second main gear 146 is locked to the lower rotating shaft S1 by a key K, so that the lower rotating shaft S2 is also rotated at the same rotational speed as that of the second main gear 146. As a result, the rotor units 200, which are coupled to the rotating shafts S1 and S2, are rotated by the rotation of the rotating shafts S1 and S2, thus executing the fluid pumping operation. In the clutch unit 100 according to another embodiment of the present invention, to further reduce the rotational speed while the rotational force is transmitted, sixth through eleventh gears and subsidiary gears (not shown) may be additionally provided beneath the fifth gear 139 and the fifth subsidiary gear 140. That is, other gears may be provided in the clutch unit 100 in the same manner as the above-mentioned gear coupling structure. Then, the rotational speed can be further reduced while the rotational force is transmitted.

Using the above-mentioned principle, in yet another embodiment, the clutch unit 100 may be a structure in which the number of gears is less than the above embodiment, so as to reduce the degree of speed reduction.

Of course, the clutch unit 100 having this structure falls within the scope of the present invention. A fourth embodiment of the clutch unit 100 of the present invention is shown in FIG. 8.

A construction of this embodiment is as follows. According to this embodiment, in the clutch unit 100 coupled to the overload prevention unit 20, a first gear 150, which engages with the helical motor gear 12 that is eccentrically positioned, is rotatably fitted over the rotating shaft S2, which is located at a position opposite the direction in which the helical motor gear 12 is offset. A first subsidiary gear 151, having a diameter larger than that of the first gear 150, is integrally provided beneath the first gear 150. A second gear 152, which has a relatively small diameter and engages with the first subsidiary gear 151, is rotatably fitted over the other rotating shaft S1. A second subsidiary gear 153, having a diameter larger than that of the second gear 152, is integrally provided beneath the second gear 152.

Furthermore, a third gear 154, which has a relatively small diameter and engages with the second subsidiary gear 153, is rotatably fitted over the rotating shaft S2. A third subsidiary gear 155, having a diameter larger than that of the third gear 154, is integrally provided beneath the third gear 154. A fourth gear 156, which has a relatively small diameter and engages with the third subsidiary gear 155, is rotatably fitted over the other rotating shaft S1. A fourth subsidiary gear 157, having a diameter larger than that of the fourth gear 156, is integrally provided beneath the fourth gear 156.

Furthermore, a drive gear 158, which has a relatively small diameter and engages with the fourth subsidiary gear 157, is fitted over and locked to the rotating shaft S2 by a key K. First and second main gears 160 and 161, having the same diameter, are respectively fitted over and locked to the rotating shafts S2 and S1 using keys K.

When the first, second, third and fourth gears 150, 152, 154 and 156 and the first, second, third and fourth subsidiary gears 151, 153, 155 and 157 are fitted over the first and second shafts S1 and S2, bearings B are interposed between them such that the gears are smoothly rotated at high speeds with respect to the rotating shafts S1 and S2. The first and second main gears 160 and 161 are rotated at high speeds by the rotational force transmitted through the drive gear 158, thus rotating the rotor units 200 at high speeds.

An operation of the fourth embodiment of the clutch unit 100 will be explained herein below with reference to FIG. 8. When the helical motor gear 12 fastened to the shaft 11 is rotated, the first gear 150, which engages with the helical motor gear 12, is rotated.

Here, the first gear 150 is rotatably fitted over the lower rotating shaft S2 (located on the left when viewing the drawing), and the first subsidiary gear 151, having a diameter larger than that of the first gear 150, is integrally provided beneath the first gear 150.

Therefore, when the first gear 150 is rotated, the first subsidiary gear 151 is rotated along with the first gear 150. The revolutions thereof are equal to each other. Simultaneously, the second gear 152, which is fitted over the upper rotating shaft S1 (located on the right when viewing the drawing), is rotated by the rotation of the first subsidiary gear 151.

At this time, when a relatively small gear is rotated by a large gear, rotational speed of the small gear is increased compared to that of the large gear, so that an increase in speed between them is realized while power is transmitted.

Therefore, in this embodiment, when power is transmitted from the first subsidiary gear 151 to the second gear 152, the rotational speed is increased.

Furthermore, because the second subsidiary gear 153, having a relatively large diameter, is integrated with the second gear 152, the number of revolutions of the second subsidiary gear 153 is equal to the number of revolutions of the second gear 152.

When the second subsidiary gear 153 is rotated, the third gear 154, which engages with the second subsidiary gear 153, is simultaneously rotated.

Because this is a condition in which a gear having a large diameter rotates a gear having a small diameter, the rotational speed is further increased when the power is transmitted between them.

As well, the third gear 154 is rotatably fitted over the lower rotating shaft S2. The third subsidiary gear 155 having a large diameter is integrated with the third gear 154, so that their revolutions are equal to each other. The fourth gear 156, which is rotatably fitted over the upper rotating shaft S1, engages with the third subsidiary gear 155.

Because the third subsidiary gear 155 has a large diameter and the fourth gear 156 has a small diameter, the rotational speed is increased when the power is transmitted between them.

Furthermore, the fourth subsidiary gear 157, having a large diameter, is integrated with the fourth gear 156, so that the fourth gear 156 and the fourth subsidiary gear 157 are rotated at the same angular speed.

The fourth subsidiary gear 157 engages with the drive gear 158 which has a small diameter and is locked to the lower rotating shaft S2 by the key. Therefore, the power is transmitted from the fourth subsidiary gear 157 having a large diameter to the drive gear 158 having a small diameter, so that the rotational speed is changed to high speed. Because the drive gear 158 is locked to the lower rotating shaft S2 (placed at the lower position when viewing the related drawing) by the key K, the rotating shaft S2 is rotated along with the drive gear 158.

Furthermore, as shown in FIG. 8, the second main gear 161, which is coaxial with the drive gear 158, is locked to the rotating shaft S2 by the key K, so that they are rotated at the same angular speed. The first main gear 160 engages with the second main gear 161, and the first and second main gears 160 and 161 have the same diameter.

Therefore, the first main gear 160 is rotated by rotation of the second main gear 161. At this time, they are rotated in directions opposite each other. Furthermore, because the first main gear 160 is locked to the upper rotating shaft S1 by the key K, the rotating shaft S1 is rotated by the rotation of the first main gear 160. As a result, the rotational speed of the rotating shaft S1 is changed to high speed by the clutch unit 100 of the fourth embodiment. The rotating shaft S2 rotates the rotor units 200 of the lower ends of the rotating shafts S1 and S2 in the state of being rotated at a high speed. As described above, the first, second, third and fourth gears 150, 152, 154 and 156 and the first, second, third and fourth subsidiary gears 151, 153, 155 and 157 are rotatably coupled to the rotating shafts S1 and S2 through the bearings B, thus executing only the function of a change of speed.

According to another embodiment, fifth through tenth gears and subsidiary gears may (not shown) be additionally provided below the fourth gear 156 and the fourth subsidiary gear 157 of FIG. 8 to further increase the rotational speed of the rotating shafts.

The clutch unit 100 of the present invention has been explained. Hereinafter, the rotor units 200, which are rotated by rotation of the rotating shafts S1 and S2 changed in speed by the clutch 100 and thus execute a function of pumping fluid, will be described in detail. A first embodiment of the rotor unit 200 is shown in FIGS. 9 through 12. A second embodiment of the rotor unit 200 is shown in FIGS. 15 and 16. First, the rotor unit 200 according to the first embodiment will be explained herein below.

According to one embodiment as shown in FIGS. 9 and 10, each rotor unit 200 of the present invention includes a cylindrical housing 230 which has a cylindrical shape with a diameter smaller than an inner diameter of the chamber 30. A plurality of bearing seats 231 (FIG. 12) is formed in a circumferential inner surface of the cylindrical housing 230. A space 235 is defined in the cylindrical housing 230. Each rotor unit 200 further includes an eccentric rotary body 220 which has a diameter smaller than the inner diameter of the cylindrical housing 230 and is eccentrically fifted over the rotating shaft S1 or S2, respectively.

Furthermore, a bearing means 210 is seated into each bearing seat 231 of the cylindrical housing 230. Both the cylindrical housing 230 and the eccentric rotary body 220 are provided in each of the upper and lower chambers 30. The two cylindrical housings 230 are coupled to each other through a cross-plate 207 and are eccentrically rotated.

As such, each of the rotor units 200 comprises the cylindrical housing 230, the eccentric rotary body 220 and the bearing means 210 provided in the cylindrical housing 230, such that the two rotor units 200 are placed in the respective chambers 30.

The rotor units 200 are placed in the chambers 30 which communicate with an inlet BC and an outlet BD are formed. Each chamber 30 may include a substantially genuine circular cross-section. Each of the rotor units 200 has the plurality of bearing seats 231.

Needle roller bearings or ball bearings are seated into the bearing seats 231 such that the rotor unit 200 is smoothly eccentrically rotated.

Hereinafter, an operation of the rotor unit 200 will be explained in detail.

As shown in FIGS. 9 through 12, the eccentric rotary bodies 220 of the rotor units 200 are fitted over the respective rotating shafts S1 and S2, which can be coupled to the clutch unit 100 according to any of the embodiments described above.

At this time, each eccentric rotary body 220 is eccentrically fitted over the corresponding rotating shaft S1, S2 but not coaxially fitted over it.

Therefore, when the rotating shafts S1 and S2 are rotated, the eccentric rotary bodies 220 are eccentrically rotated.

The eccentric rotary bodies 220 move along the circumferential inner surfaces of the chambers 30 in order to draw and discharge fluid into and from the pump.

As shown in the drawings, when the eccentric rotary body 220, which is disposed at an upper position, is rotated in a clockwise direction, the lower eccentric rotary body 220 is rotated in a counterclockwise direction. Each rotating shaft S1, S2 is coaxially provided in each chamber 30, and each eccentric rotary body 220 is eccentrically fitted over each rotating shaft S1, S2.

Therefore, when the eccentric rotary body 220 is rotated, a moving track of a portion of the eccentric rotary body 220 which is farthest from the rotating shaft is configured in a predetermined shape. That is, the moving track is formed along the circumferential inner surface of the chamber 30.

To ensure smooth movement of the eccentric rotary body 220, the needle roller bearings or ball bearings are seated into the bearing seats 231 formed in the circumferential inner surface of the cylindrical housing 230.

Therefore, the circumferential outer surface of the eccentric rotary body 220 is in rolling contact with the needle roller bearings or ball bearings, while the eccentric rotary body 220 is rotated. Meanwhile, the eccentric rotary body 220 is provided in each of the upper and lower rotor units 200. When the upper rotating shaft S1 is rotated in a clockwise direction, the eccentric rotary body 220 fitted over the upper rotating shaft S1 is also rotated in a clockwise direction, as shown in FIGS. 9 and 10.

In detail, in a state in which the upper rotor unit 200 contacts the uppermost portion of the circumferential inner surface of the upper chamber 30 and the rotor units 200 are placed at a vertical line, as shown in FIG. 9, if the rotating shaft S1 is rotated in a clockwise direction, the associated eccentric rotary body 220 is also rotated in a clockwise direction. At this time, the bearing means (ball bearings or needle roller bearings) ensures smooth rotation.

Rotation of the rotor units 200 will be described in detail herein below. Referring to FIG. 9, in a state in which the rotor units 200 are placed upright in the chambers, when the upper eccentric rotary body 220 is rotated in a clockwise direction at 90°, a contact surface of the upper rotor unit 200 moves to a portion of the inner surface of the upper chamber 30 which is substantially in a 3 o'clock direction, that is, the portion angularly spaced apart from the uppermost point at substantially 90°. Simultaneously, the lower eccentric rotary body 220 is rotated in a counterclockwise direction, so that a contact surface of the lower rotor unit 200 moves to a portion of the inner surface of the lower chamber 30 which is substantially in a 9 o'clock direction, that is, the portion angularly spaced apart from the uppermost point at substantially 270°. When the upper eccentric rotary body 220 is further rotated from the state shown in the second view of FIG. 9 in a clockwise direction, the contact surface of the upper rotary unit 200 moves to a lowermost portion of the upper chamber 30 which is substantially in a 6 o'clock direction, that is, the portion angularly spaced apart from the uppermost point at substantially 180°. Simultaneously, the lower eccentric rotary body 220 is also further rotated in a counterclockwise direction, so that the contact surface of the lower rotary unit 200 moves to a portion of the inner surface of the lower chamber 30 which is substantially in a 6 o'clock direction, that is, the portion angularly spaced apart from the uppermost point at substantially 180° (see, the first view of FIG. 10).

Subsequently, when the upper eccentric rotary body 220 is further rotated from the state shown in the first view of FIG. 10 in a clockwise direction, the contact surface of the upper rotary unit 200 moves to the lowermost portion of the upper chamber 30 which is substantially in a 9 o'clock direction, that is, the portion angularly spaced apart from the uppermost point at substantially 270°. Simultaneously, the lower eccentric rotary body 220 is also further rotated in a counterclockwise direction, so that the contact surface of the lower rotary unit 200 moves to a portion of the inner surface of the lower chamber 30 which is substantially in a 3 o'clock direction, that is, the portion angularly spaced apart from the uppermost point at substantially 90°. Thereafter, the process is returned to the first step. As such, the process is continuously repeated, so that fluid is pumped by movement of the rotor units 200.

When the rotor units 200 are placed at positions shown in the first view of FIG. 9, the distance between the contact point between the upper eccentric rotary body 220 and the upper cylindrical housing 230 and the contact point between the lower eccentric rotary body 220 and the lower cylindrical housing 230 is shortest, as described above with reference to FIG. 4.

In other words, this means that the distance between the contact points between the eccentric rotary bodies 220 and the cylindrical housings 230 of the upper and lower rotor units 200 is shortest. Of course, the distance between the rotating shafts S1 and S2, over which the eccentric rotary bodies 220 are fitted, are constant without being varied.

When the rotor units 200 are placed at positions shown in the second view of FIG. 9 by rotation of the rotating shafts S1 and S2, the distance between the contact points between the eccentric rotary bodies 220 and the cylindrical housings 230 becomes longest, as described above with reference to FIG. 4.

In other words, the contact points between the eccentric rotary bodies 220 and the cylindrical housings 230 of the upper and lower rotor units 200 are farthest away from each other.

However, the positions of the rotating shafts S1 and S2 cannot be still changed.

Here, it is an important issue how to compensate for the distance difference. To achieve the above-mentioned purpose, embodiments of the present invention is designed such that the diameter of each eccentric rotary body 220 is smaller than the inner diameter of each cylindrical housing 230.

Therefore, as shown in the drawings, the space 235 is defined between them such that the eccentric rotary body 220 is movable in the space 235.

Thus, the distance difference is compensated for by the space 235 while each eccentric rotary body is rotated in the space 235 of each cylindrical housing 230. Furthermore, in one embodiment as shown in FIGS. 11 and 12, to ensure smoother movement of the eccentric rotary bodies 220 in the cylindrical housings 230, the bearing seats 231 are formed in the inner surface of the cylindrical housings 230, and it is constructed such that the bearing seats 231 have different depths.

That is, the bearing seats 231 are symmetrically formed along the inner surface of the cylindrical housing 230 and have different depths which are deeper in the order of Gxa<G3 a<G2 a<Gla<Gya.

In detail, as shown in FIG. 12, the bearing seat Gya, which is formed at the uppermost position of the cylindrical housing 230, is deepest. The bearing seat G1 a, which is formed at a position spaced apart from the uppermost position at a predetermined angular interval, is shallower than the bearing seat Gya. The depths of the remaining bearings are shallower in the order of G2 a>G3 a>Gxa.

Thus, when the ball bearings or needle roller bearings are inserted into the bearing seats 231, as shown in FIG. 11, the ball bearing or needle roller bearing seated into the bearing seat Gya protrudes at the lowest height, and the ball bearings or needle roller bearings seated into the bearing seats Gxa protrude at the highest height.

Therefore, a track, along which the eccentric rotary body 220 contacts the ball bearings or needle roller bearings protruding from the inner surface of the cylindrical housing 230, has at an upper portion thereof an at least partially elliptical shape and at a lower portion thereof an at least partially circular shape having a relatively small curvature, as shown in FIG. 13.

The effect of this construction will be easily appreciated with reference to FIG. 13. That is, the rotor unit 200 moves while the distance difference induced in the cross-plate 207 of the rotor unit 200 is compensated for by the space 235 defined in the rotor unit 200. When the eccentric rotary body 220 is placed at positions corresponding to the bearing seats Gxa, in other words, when the eccentric rotary body 220 is placed in between a 3 o'clock direction and a 9 o'clock direction, the eccentric rotary body 220 contacts the ball bearings or needle roller bearings which protrude to greater heights from the inner surface of the cylindrical housing 230.

As shown in the second view of FIG. 13, when the eccentric rotary body 220 is in a 6 o'clock direction, because the ball bearings or needle roller bearings, which are seated into the bearing seats Gxa, protrude at greater heights, there is an advantage in that the circumferential outer surface of the cylindrical housing 230 can contact and seal a passage more securely.

This effect provides more superior pumping performance.

As shown in FIG. 11, the bearing seats Gya, G1 a, G2 a, G3 a and Gxa are symmetrical with each other based on a Y-axis.

In detail, the bearing seats formed at an upper portion are symmetrical based on the Y-axis, and the remaining bearing seats Gxa formed at a lower portion have the same depth.

As such, the bearing seats are formed in shapes and to depths shown in FIG. 11.

One of ordinary skill in the art will appreciate that the above-mentioned effect may be realized both by bearing seats having different diameter, and by ball bearings, which have the diameters corresponding to the bearing seats and are seated into the bearing seats.

That is, as shown in FIG. 14, the bearing seats 231 have different diameters which are larger in the order of Mya<M1 a<M2 a<M3 a<Mxa. When sectioning the cylindrical housing into upper and lower portions, the bearing seats Mxa formed at the lower portion have the same diameter. Furthermore, each bearing means, which is seated into each bearing seat, has the same diameter as that of the associated bearing seat.

In other words, a height at which each bearing means, such as ball bearings or needle roller bearing, protrudes from the bearing seat is varied depending on the diameter of the bearing means.

As such, when the ball bearings having diameters corresponding to the respective bearing seats are seated into the bearing seats, the diameters of which are larger in the order of Mya<M1 a<M2 a<M3 a<Mxa as the diameter of the bearing seats is increased, the protruding height of a ball bearing seated in the larger bearing seat is greater than the others.

In other words, the heights at which the ball bearings protrude are higher in the same order as that of the bearing seats, the diameters of which are larger in the order of Mya<M1 a<M2 a<M3 a<Mxa.

This structure also falls within the scope of the present invention.

As described in brief above, in embodiments of the present invention, various types of bearing means 210 may be seated into the bearing seats 231.

For example, ball bearings or needle roller bearings may be used as the bearing means 210.

If ball bearings are used as the bearing means, a plurality of ball bearings is seated into each bearing seat 231. If needle roller bearings, each having a predetermined length, are used as the bearing means, a single needle roller bearing is seated into each bearing seat 231.

It may be preferable that the ball bearings be used for pumping fluid, such as water having a low viscosity, and the needle roller bearings be used for pumping fluid, such as mud having a high viscosity.

A second embodiment of the rotor unit 200 is shown in FIGS. 15 and 16. Hereinafter, the second embodiment will be explained in detail with reference to these drawings. In the second embodiment of the rotor unit 200, each rotor unit 200 includes a cylindrical housing 230 which has a cylindrical shape with a diameter smaller than an inner diameter of the chamber 30. A space 260 is defined in the cylindrical housing 230. Each rotor unit 200 further includes an eccentric rotary body 220 which has a diameter smaller than the inner diameter of the cylindrical housing 230 and is eccentrically fitted over the rotating shaft S1 or S2, respectively. A plurality of bearing seats 271 is formed in a circumferential outer surface of each eccentric rotary body 220.

Furthermore, a bearing means 210 is seated into each bearing seat 271 of the eccentric rotary body 220.

Both the cylindrical housing 230 and the eccentric rotary body 220 are provided in each of the upper and lower chambers 30. The two cylindrical housings 230 are coupled to each other through a cross-plate 207 and are eccentrically rotated.

As such, the general construction of the rotor unit 200 according to the second embodiment, except for the bearing seats 271 formed in the circumferential outer surface of the eccentric rotary body 220, remains substantially the same as the rotor unit 200 according to the first embodiment.

The bearing means 210 is seated into each bearing seat 271 of the eccentric rotary bodies 220. The bearing means 210 serves to provide a smoother rotation of each eccentric rotary body 220 in each cylindrical housing 230.

Furthermore, the pumping operation of the rotor unit 200 of the second embodiment is executed in substantially the same manner as that of the first embodiment. Therefore, further explanation is deemed unnecessary.

Meanwhile, in the second embodiment, the bearing seats 271 are symmetrically formed in the outer surface of the eccentric rotary body 220 and have different depths, which are deeper in the order of Fya<F3 a<F2 a<Fla<Fxa.

That is, unlike the first embodiment, the bearing seats 271 are formed along the circumferential outer surface of the eccentric rotary body 220 and spaced apart from each other at regular angular intervals. As shown in FIG. 16, of the bearing seats 271, the bearing seats Fxa are deepest.

That is, the bearing seats Fxa, which are formed at positions spaced apart from the uppermost point at substantially 90°, are deepest. The remaining bearing seats, which are formed at positions spaced apart from each other at regular angular intervals, are shallower in the order of F1 a>F2 a>F3 a>Fya.

In conclusion, the bearing seats Fxa are deepest, and the bearing seats Fya are shallowest.

Furthermore, the two bearing seats 271, which are formed in the outer surface of the eccentric rotary body 220 at symmetrical positions based on the center of the eccentric rotary body 220 (at positions spaced apart from each other at substantially 180°), have the same depth. Therefore, when the bearing means 210 is seated into each bearing seat 271, it is configured in a shape shown in FIG. 15.

As shown in the drawing, the protruding height of the bearing means (the ball bearings or the needle roller bearing), which is seated into the bearing seat Fxa which is substantially in a 3 o'clock direction, that is, formed in the eccentric rotary body 220 at a position spaced apart from the uppermost point at substantially 90°, is lowest. The protruding height of the bearing means 210 (the ball bearings or the needle roller bearing), which is seated into the bearing seat Fya which is substantially in a 12 o'clock direction, that is, formed in the eccentric rotary body 220 at the uppermost position, is highest.

According to one embodiment, a modification of the second embodiment is shown in FIG. 17. This modification, in which bearing seats have different diameters and bearing means seated into the bearing seats also have different diameters, has substantially the same effect as that of the second embodiment. This modification is as follows. The bearing seats 271, which are formed in each eccentric rotary body, have diameters which are larger in the order of Nxa<N1 a<N2 a<N3 a<Nya. Each bearing means 210, which is seated into each bearing seat 271, has the same diameter as that of the associated bearing seat 271. Furthermore, the bearing seats 271 are symmetrically formed along the circumferential outer surface of the eccentric rotary body 220.

Of course, as the diameters of the bearing seats 271 are increased, the diameter of the bearing means 210 seated into the bearing seats 271 becomes increased, so that the protruding height of the bearing means 210 also becomes increased.

This modification has the same outline as that of the above-mentioned embodiment and, thus, the effect thereof is also substantially equal to the above-mentioned embodiment.

The outline of the eccentric rotary body 220 which is defined by the bearing means 210 will be explained herein below. As shown in FIG. 18, the outline of the eccentric rotary body 220, which is defined by connecting the outermost points of the ball bearings or needle roller bearings that protrude from the bearing seats 271, is configured in an elliptical shape.

Here, the eccentric rotary body 220 having the elliptical outline is eccentrically fitted over the rotating shaft, which is rotated in place.

Therefore, as shown in FIG. 15 or 18, when the eccentric rotary body 220 is rotated, the bearing means 210 (the ball bearings or needle roller bearing), which is seated into the uppermost bearing seat 271 having dimension Fya, mainly contacts the inner surface of the cylindrical housing.

When the eccentric rotary body is rotated at substantially 90° and thus enters the state of the second view of FIG. 18, it is configured in an elliptical shape having a horizontal major axis.

Subsequently, when the eccentric rotary body is rotated at substantially 180° and, thus, oriented in substantially a 6 o'clock direction, it compresses the portion of Fya having the shallowest depth, as shown in the third view of FIG. 18.

Here, because the bearing seat 271 having dimension Fya has the shallowest depth, the height at which the ball bearings or needle roller bearing protrudes from the bearing seat 271 is highest. Thereby, when the eccentric rotary body 220 is in the above-mentioned state, the eccentric rotary body 220 most securely pushes downwards the cylindrical housing 230.

Therefore, in the state shown in the last view of FIG. 18, the eccentric rotary body 220 serves to reliably close the passage formed below it, thus maximizing the pumping performance of the pump.

Meanwhile, ball bearings or needle roller bearings can be used as the bearing means 210 according to the second embodiment, in substantially the same manner as that of the first embodiment. Furthermore, it is preferred that angular intervals, at which the ball bearings or needle roller bearings are spaced apart from each other, are determined depending on a difference between the diameter of the space 235 of the cylindrical housing 230 and the outer diameter of the outline of the eccentric rotary body 220. To easily illustrate this concept, FIG. 19 shows the elements with an exaggerated size difference between them. As shown in the drawing, if the diameter of the eccentric rotary body 220 is very small compared to the space 235 defined in the cylindrical housing 230, when the eccentric rotary body 220 is rotated along the inner surface of the cylindrical housing 230 from the state in which the uppermost ball bearing or needle roller bearing P contacts the inner surface of the cylindrical housing 230, a subsequent contact point becomes the point T. In other words, the contact points P and T are very close.

Here, as the diameter of the eccentric rotary body 220 becomes smaller, the distance between the contact points is reduced. Conversely, as shown in FIG. 20, if the diameter of the eccentric rotary body 220 is large to the degree similar to the size of the space 235 of the cylindrical housing 230, when the eccentric rotary body 220 is rotated along the inner surface of the cylindrical housing 230 from the state in which the uppermost ball bearing or needle roller bearing P contacts the inner surface of the cylindrical housing 230, a subsequent contact point becomes the point T of FIG. 20.

As such, the distance between the adjacent contact points P and T is increased compared to the case of FIG. 19.

Accordingly, as the diameter of the eccentric rotary body 220 is reduced, the number of required ball bearings or needle roller bearings is increased. As the diameter of the eccentric rotary body 220 is increased, the number of required ball bearings or needle roller bearings is reduced.

FIGS. 21 through 29 illustrate various embodiments incorporating distinct structures for the chamber 30. For example, one through ten pairs of upper and lower chambers 30, each having the rotor unit 200 therein, may be constructed in a row to form a multiple structure.

The term ‘multiple structure’ means that several rotor units 200 and chambers 30 may be provided on each of the upper and lower rotating shafts.

In detail, in the multiple rotary pump according to an embodiment of the present invention, a plurality of chambers 30 is disposed in a row. Separation plates are interposed between the chambers 30, so that the chambers 30 are divided. The upper rotors units 200 and the lower rotor units 200, which are provided in the chambers 30, are respectively fitted over the single upper rotating shaft S1 and the single lower rotating shaft S2, respectively. The upper rotors units 200 and the lower rotor units 200, which are respectively fitted over the upper and lower rotating shafts S1 and S2 and are provided in the chambers 30, are arranged such that they differ in phase. The upper and lower rotating shafts S1 and S2 receive power from the drive motor through the clutch unit. Each of the upper and lower rotor units 200 may have a structure of the rotor unit 200 as described above according to the first or second embodiment.

In an embodiment of the multiple rotary pump of the present invention, as described above, because no torsional stress is applied to the upper rotating shaft S1 and the lower rotating shaft S2, even when the upper and lower rotor units 200, which are respectively provided on the upper and lower rotating shafts S1 and S2 and have different phases, are rotated, they are not damaged. Furthermore, even if the upper and lower rotating shafts S1 and S2 are rotated at high speeds, because they are stable, the upper and lower rotor units 200 can be stably rotated at high speeds.

Furthermore, referring to FIGS. 21 through 29, in the multiple rotary pump having the above-mentioned construction and operation, manifolds may be coupled to inlets BC and outlets BD of the chambers 30. In this case, a mixture ratio of two or more kinds of fluid, which is drawn into the chambers 30 and discharged from the chambers 30, can be controlled.

For example, as shown in FIG. 25, a first manifold CQ is coupled to inlets BC of first, second and third chambers CA, CB and CC, and a separate inlet pipe CF is coupled to an inlet BC of a fourth chamber CD.

Then, objective fluid is drawn into the first, second and third chambers CA, CB and CC through the first manifold, while diluent (water or chemical) is drawn into the fourth chamber CD through the inlet pipe. Both the objective fluid and the diluent are discharged from the chambers 30 through a second manifold CT coupled to the outlets of the chambers 30. Therefore, a mixture ratio of diluent to objective fluid to be discharged through the second manifold CT can be constantly controlled.

According to another embodiment as shown in FIG. 26, a multiple rotary pump may be constructed such that a third manifold DA is coupled to the inlets of the first and second chambers CA and CB and a fourth manifold DB is coupled to the inlets of the third and fourth chambers CC and CD.

In FIG. 26, the reference character CT denotes a second manifold coupled to the outlets of the chambers.

Furthermore, in other embodiments, as shown in FIG. 27 or 28, the multiple rotary pump may be constructed such that a fifth manifold FA is coupled to the outlets BD of the first, second and third chambers CA, CB and CC and a separate outlet pipe FB is coupled to the outlet of the fourth chamber CD or, alternatively, a sixth manifold GA is coupled to the outlets BD of the first and second chambers and a seventh manifold GB is coupled to the outlets BD of the third and fourth chambers CC and CD.

Thereby, objective fluid discharged from the first, second, third and fourth chambers CA, CB, CC and CD can be divided in a desired ratio.

According to one embodiment, the overload prevention unit 20 is provided between the output shaft 11 of the drive motor 10 and the clutch shaft, as shown in FIGS. 4, 5, 6, 30 and 31.

In one embodiment, the overload prevention unit 20 comprises a plurality of ball seats 21, which are formed in a circumferential outer surface of an end of the output shaft of the drive motor 10, and a coupler 24 which is coupled to the clutch unit 100, with a receiving space 22 defined in the coupler 24. The output shaft 11 is inserted into the receiving space 22. A plurality of ball insertion holes 23 are formed along a sidewall of the coupler 24 at positions corresponding to the ball seats 21.

Furthermore, a cover ring 26, which is made of synthetic resin, is fitted over a circumferential outer surface of the coupler 24 to prevent balls 25 (FIG. 31) from being undesirably removed.

Therefore, each ball 25 is inserted into each ball insertion hole 23 and seated into each ball seat 21. The balls 25 are covered with the cover ring 26. When an overload is applied to the clutch unit 100, the balls 25 are removed from the ball seats 21 while pushing outwards the cover ring 26, thus preventing power from being transmitted.

The end of the output shaft 11 of the drive motor 10 is tapered, and the ball seats 21 are formed in the circumferential outer surface of the end of the output shaft 11.

The helical motor gear 12 is provided on an end of the coupler 24, which has the receiving space 22 into which the end of the output shaft 11 of the drive motor 10 is inserted. The ball insertion holes 23, which are formed the sidewall of the coupler at positions corresponding to the ball seats 21, communicate with the receiving space 22.

Therefore, when the coupler 24 is coupled to the output shaft of the drive motor 10 after the balls are inserted into the ball insertion holes 23, the balls 25 are seated into the ball seats 21.

Furthermore, because the cover ring 26 is fitted over the coupler 24, the balls 25 are stopped by the inner surface of the cover ring 26, thus being prevented from being undesirably removed from the coupler 24, and maintaining the state of being reliably seated into the ball seats 21. Therefore, the coupler 24 reliably couples the drive motor 10 to the clutch unit 100 such that, when the drive motor 10 is rotated, power is securely transmitted.

However, if an overload is applied to the drive motor 10 due to rubble or a foreign substance having high hardness being trapped in the rotor unit 200 or the clutch unit 100, the coupler 24, which couples the clutch unit 100 to the output shaft 11 of the drive motor 10, can no longer rotate and must submit to the overload. At this time, if the overload is increased, the balls 25 push the cover ring 26 made of synthetic resin outwards and are thus removed from the ball seats 21.

As such, embodiment of the present invention having the overload prevention unit 20 can solve a problem of breakage in the clutch unit 100, which has been frequently induced in the conventional pumps.

That is, in the conventional pumps, in the above-mentioned condition of an overload, there is a problem in that gear teeth of the clutch unit 100 are damaged by an overload applied to the gear teeth. However, the present invention can solve this problem using the overload prevention unit 20.

The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure. 

1. A rotary pump comprising: a drive motor; upper and lower chambers; a pair of rotor units respectively provided in the upper and lower chambers such that the pair of rotor units are configured to be driven by the drive motor and moving along inner surfaces of the chambers; a cross-plate integrally connecting the pair of rotor units to each other, wherein each of the rotor units includes: a cylindrical housing; an eccentric rotary body installed and eccentrically rotatable in the cylindrical housing; and means for reducing friction between the eccentric rotary body and the cylindrical housing when the eccentric rotary body rotates within the cylindrical housing.
 2. The rotary pump as claimed in claim 1, wherein the cylindrical housing includes a cylindrical shape with a diameter smaller than an inner diameter of each chamber, with a plurality of bearing seats formed in a circumferential inner surface of the cylindrical housing, and a space defined in the cylindrical housing, the eccentric rotary body having a diameter smaller than the inner diameter of the cylindrical housing and eccentrically fitted over a rotatable shaft, and the means for reducing friction includes a plurality of bearing members respectively seated into the plurality of bearing seats of the cylindrical housing.
 3. The rotary pump as claimed in claim 2, wherein the bearing seats each have a depth, respective magnitudes of the depths sequentially decreasing from a 12 o'clock position to a 3 o'clock position, being substantially constant from the 3 o'clock position to a 9 o'clock position, and sequentially increasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential inner surface of the cylindrical housing.
 4. The rotary pump as claimed in claim 3, wherein when the cylindrical housing is sectioned into a center side half-circle portion which is adjacent the cross-plate and a remaining outside half-circle portion, the bearing seats formed in the center side half-circle portion of the cylindrical housing have a most shallow depth with respect to the other bearing seats, the center side half-circle portion extending from the 3 o'clock position to the 9 o'clock position.
 5. The rotary pump as claimed in claim 2, wherein the bearing seats each have a diameter, respective magnitudes of the diameters sequentially increasing from a 12 o'clock position to a 3 o'clock position, being substantially constant from the 3 o'clock position to a 9 o'clock position, and sequentially decreasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential inner surface of the cylindrical housing.
 6. The rotary pump as claimed in claim 5, wherein when the cylindrical housing is sectioned into a center side half-circle portion which is adjacent the cross-plate and a remaining outside half-circle portion, the bearing seats formed in the center side half-circle portion of the cylindrical housing have a most largest diameter with respect to the other bearing seats, the center side half-circle portion extending from the 3 o'clock position to the 9 o'clock position.
 7. The rotary pump as claimed in claim 1, wherein the cylindrical housing includes a cylindrical shape with a diameter smaller than an inner diameter of each chamber, with a space defined in the cylindrical housing, the eccentric rotary body having a diameter smaller than the inner diameter of the cylindrical housing and eccentrically fitted over a rotatable shaft, with a plurality of bearing seats formed in a circumferential outer surface of the eccentric rotary body, and the means for reducing friction includes a plurality of bearing members respectively seated into the plurality of bearing seats of the eccentric rotary body.
 8. The rotary pump as claimed in claim 7, wherein the bearing seats each have a depth, respective magnitudes of the depths sequentially increasing from a 12 o'clock position to a 3 o'clock position, sequentially decreasing from the 3 o'clock position to a 6 o'clock position, sequentially increasing from the 6 o'clock position to a 9 o'clock position, and sequentially decreasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential outer surface of the eccentric rotary body.
 9. The rotary pump as claimed in claim 8, wherein when the cylindrical housing is sectioned into a left side half-circle portion and a right side half-circle portion by a line which is extended along a longitudinal direction of the cross-plate, the left side half-circle portion and the right side half-circle portion are symmetrically formed along the circumferential outer surface of the eccentric rotary body.
 10. The rotary pump as claimed in claim 8, wherein the bearing seats each have a diameter, respective magnitudes of the diameters sequentially decreasing from a 12 o'clock position to a 3 o'clock position, sequentially increasing from the 3 o'clock position to a 6 o'clock position, sequentially decreasing from the 6 o'clock position to a 9 o'clock position, and sequentially increasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential outer surface of the eccentric rotary body.
 11. The rotary pump as claimed in claim 10, wherein when the cylindrical housing is sectioned into a left side half-circle portion and a right side half-circle portion by a line which is extended along a longitudinal direction of the cross-plate, the left side half-circle portion and the right side half-circle portion are symmetrically formed along the circumferential outer surface of the eccentric rotary body.
 12. The rotary pump to as claimed in claim 1, wherein the means for reducing friction includes ball bearings or needle roller bearings positioned between the cylindrical housing and the eccentric rotary body.
 13. The rotary pump as claimed in claim 1, wherein the rotary pump further comprises an overload prevention unit provided on an output shaft of the drive motor in order to prevent the drive motor from overloading.
 14. The rotary pump as claimed in claim 13, wherein the overload prevention unit comprises: a plurality of ball seats formed in a circumferential outer surface of an end of the output shaft of the drive motor; a coupler having a receiving space in which the output shaft is inserted and a plurality of ball insertion holes formed along a sidewall of the coupler at positions corresponding to the ball seats; and a cover ring fitted over a circumferential outer surface of the coupler to prevent balls from being undesirably removed, wherein the balls are inserted into the ball insertion holes and seated into the ball seats, and the cover ring surrounds the balls, so that, when an overload is applied to the clutch unit, the balls push outwards and deform the cover ring thus interrupting power transmission.
 15. The rotary pump as claimed in claim 4, wherein a motor gear is formed on a circumferential outer surface of the coupler, wherein the motor gear is a helical gear.
 16. The rotary pump as claimed in claim 1, wherein the rotary pump further comprises a power transmitting, unit in order to transmit power from the drive motor to the rotor units, wherein a rotational speed of the drive motor is changed by the power transmitting unit.
 17. The rotary pump as claimed in claim 16, wherein the power transmitting unit comprises: a pair of rotatable shafts which are parallel to each other; a drive gear rotatable engaging with a motor gear formed on an end of an output shaft of the drive motor, and fitted on either one of the rotatable shafts; a first main gear fitted on either one of the rotatable shafts which is rotatable together with the drive gear; and a second main gear engaging with the first main gear and fitted on the other rotatable shaft wherein the first main gear and the second main gear are rotatable in an opposite direction to each other.
 18. The rotary pump as claimed in claim 16, wherein the power transmitting unit comprises: a pair of rotatable shafts which are parallel to each other; a first transmitting gear engaging with a motor gear formed on an end of an output shaft of the drive motor and idly inserted on either one of the rotatable shafts, the first transmitting gear being integrally formed with a subsidiary transmitting gear which has a diameter smaller than the diameter of the first transmitting gear; a second transmitting gear fitted on either one of the rotatable shafts or the other of the rotatable shafts; a first main gear fitted on the rotatable shaft which is rotatable together with the drive gear; a second main gear engaging with the first main gear and fitted on the rotatable shaft on which the first main gear is not fitted; and a plurality of driven gears arranging between the subsidiary transmitting gear and the second transmitting gear and transmitting power from the subsidiary transmitting gear to the second transmitting gear, the driven gears being integrally formed with respective subsidiary driven gears which have a diameter smaller than the diameter of the driven gears, wherein each of the driven gears is idly inserted on the rotatable shafts such that a downstream driven gear is rotatably engaged with an upstream subsidiary driven gear, and the first main gear and the second main gear are rotatable in an opposite direction to each other.
 19. The rotary pump as claimed in claim 16, wherein the power transmitting unit comprises: a pair of the rotatable shafts which are parallel to each other; a first transmitting gear engaging with a motor gear formed on an end of an output shaft of the drive motor and idly inserted on either one of the rotatable shafts, the first transmitting gear being integrally formed with a subsidiary transmitting gear which has a diameter larger than the diameter of the first transmitting gear; a second transmitting gear fitted on either one of the rotatable shafts or the other of the rotatable shafts; a first main gear fitted on the rotatable shafts which is rotatable together with the drive gear; a second main gear engaging with the first main gear and fitted on the rotatable shaft on which the first main gear is not fitted; and a plurality of driven gears arranging between the subsidiary transmitting gear and the second transmitting gear and transmitting power from the subsidiary transmitting gear to the second transmitting gear, the driven gears being integrally formed with respective subsidiary driven gears which have a diameter larger than the diameter of the driven gears, wherein each of the driven gears is idly inserted on the rotatable shafts such that a downstream driven gear is rotatably engaged with an upstream subsidiary driven gear, and the first main gear and the second main gear are rotatable in an opposite direction to each other.
 20. A rotary pump comprising: a drive motor; a plurality of upper and lower chambers which are laterally arranged to each other; a plurality of pairs of rotor units respectively provided in the respective upper and lower chambers such that the pairs of rotor units are configured to be driven by the drive motor and moving along inner surfaces of the chambers; and a cross-plate integrally connecting the pairs of rotor units to each other, wherein each of the rotor units includes: a cylindrical housing; an eccentric rotary body installed and eccentrically rotatable in the cylindrical housing; and means for reducing friction between the eccentric rotary body and the cylindrical housing when the eccentric rotary body rotates within the cylindrical housing. 